Whispering gallery modes in a bent ZnO microwire

Micro-cavities play an important role in the light-matter interaction. The cross section of wurtzite-structured ZnO microwire is a hexagon, which gives a high quality factor. Exciton-polariton, micro-and nanowire lasers and polariton condensation have been investigated using the micro-cavities of ZnO microwires at room temperature. Strain, which changes the dielectric index of a material, is one of the methods to tune the interaction between the light and the matter. In this work, the photoluminescence spectra of strain free and bent ZnO microwires are measured across the wires, and the modes shifts are observed only in the bent one near the band edge. Shifting of the cavity modes across the wire can be observed in both TE and TM polarized spectra. For a bent ZnO microwire, the microcavity can be modified by the strain from bending, and the exciton energies may shift due to the strain. The shifted exciton energy induces a change of dielectric constant, resulting in the shifting of the cavity modes across the microwire.